This invention relates to packet switched multiplexed data/voice communication systems and, in particular, to a method and apparatus for testing a subscriber's line in such a system by establishing loopbacks at various locations along the line.
Packet switched multiplexed data/voice communication systems are being looked to by telephone operating companies as one way of providing an efficient, high quality DATA and voice frequency VF signal transport capability to their subscribers. In systems of this type, the DATA and VF signals from the subscriber data terminal equipment and the subscriber telephone set are multiplexed in a remote data/voice multiplexor at the subscriber location and the multiplexed signal is coupled onto the subscriber's telephone line or loop. In the telephone central office, a central office data voice multiplexor receives the multiplexed signal on the subscriber loop and acts to separate the VF and DATA signals. The VF signal is then terminated in a normal voice switch, while the DATA signal is fed to a statistical multiplexor. The statistical multiplexor assembles the signal into appropriate form for transmission to a packet switch which continues routing of the data in packetized form to its appropriate location.
Usually the packet switch is fed by a number of other statistical multiplexors and the system includes a number of packet switches of this type. Overall system control is provided by a network control center which is responsible for system maintenance, billing, data management and other supervisory functions.
For a packet switched multiplexed data/voice system of the above type to reach a large segment of existing telephone subscribers, it is essential that the system be designed in a way to reduce cost and complexity, while still maintaining the present high level of service. One way of reducing cost in such a system is to effect testing and maintenance of subscriber lines in a way which eliminates or minimizes the need for craft personnel. Thus, when testing a subscriber line for faults if the location of the faults can be isolated to different parts of the line without sending craft personnel out to investigate the entire line, considerble savings can be realized. Furthermore, if simple on-site diagnostic equipment can be provided at the subscriber end of the line, subscriber participation in testing becomes possible and any testing by craft personnel is facilitated.
Present day procedures for isolating faults along various sections of a transmission line depend upon the use of coded information, tones or other special signals. These signals provide a mechanism for developing loopbacks at various points on the line. The loopbacks, in turn, isolate segments of the line and, therefore, provide the desired fault location and isolation. In implementing the aforementioned loopback procedures, however, added signal generating and detecting equipment is required. This adds to the complexity of the system and reduces the gains which result from minimizing the need for craft personnel.
It is therefore an object of the present invention to provide a packet switched multiplexed data/voice communication system and method, and components thereof, for realizing subscriber line testing and maintenance in a manner which avoids the need for additional complex signal generating and detecting equipment.
It is a further object of the present invention to provide a packet switched multiplexed data/voice communication system and method, and components thereof, which permit line maintenance and testing, including fault location, through a unique loopback arrangement.
It is yet a further object of the present invention to provide an on-site diagnostic block for use in a packet switched multiplexed data/voice communication system.